我正在尝试使NSTask运行这样的命令:
ps -clx | grep'Finder'| awk'{print $ 2}'
这是我的方法
- (void) processByName:(NSString*)name {
NSTask *task1 = [[NSTask alloc] init];
NSPipe *pipe1 = [NSPipe pipe];
[task1 waitUntilExit];
[task1 setLaunchPath: @"/bin/ps"];
[task1 setArguments: [NSArray arrayWithObjects: @"-clx", nil]];
[task1 setStandardOutput: pipe1];
NSTask *task2 = [[NSTask alloc] init];
NSPipe *pipe2 = [NSPipe pipe];
[task2 setLaunchPath: @"/usr/bin/grep"];
[task2 setArguments: [NSArray arrayWithObjects: @"'Finder'", nil]];
[task2 setStandardInput:pipe1];
[task2 setStandardOutput: pipe2];
NSTask *task3 = [[NSTask alloc] init];
NSPipe *pipe3 = [NSPipe pipe];
[task3 setLaunchPath: @"/usr/bin/grep"];
[task3 setArguments: [NSArray arrayWithObjects: @"'{print $2}'", nil]];
[task3 setStandardInput:pipe2];
[task3 setStandardOutput: pipe3];
NSFileHandle *file = [pipe3 fileHandleForReading];
[task1 launch];
[task2 launch];
[task3 launch];
NSData *data;
data = [file readDataToEndOfFile];
NSString *string;
string = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
NSLog(@"Result: %@", string);
}
但是结果只是
结果:
我在做什么错?
编辑
- (void) processByName:(NSString*)name {
NSTask *task1 = [[NSTask alloc] init];
NSPipe *pipe1 = [NSPipe pipe];
[task1 waitUntilExit];
[task1 setLaunchPath: @"/bin/ps"];
[task1 setArguments: [NSArray arrayWithObjects: @"-clx", nil]];
[task1 setStandardOutput: pipe1];
NSTask *task2 = [[NSTask alloc] init];
NSPipe *pipe2 = [NSPipe pipe];
[task2 setLaunchPath: @"/usr/bin/grep"];
[task2 setArguments: [NSArray arrayWithObjects: @"'Finder'", nil]];
[task2 setStandardInput:pipe1];
[task2 setStandardOutput: pipe2];
NSTask *task3 = [[NSTask alloc] init];
NSPipe *pipe3 = [NSPipe pipe];
[task3 setLaunchPath: @"/usr/bin/grep"];
[task3 setArguments: [NSArray arrayWithObjects: @"'{print $2}'", nil]];
[task3 setStandardInput:pipe2];
[task3 setStandardOutput: pipe3];
NSFileHandle *file = [pipe3 fileHandleForReading];
[task1 launch];
[task2 launch];
[task3 launch];
[[NSNotificationCenter defaultCenter] addObserverForName:NSTaskDidTerminateNotification
object:task3
queue:nil
usingBlock:^(NSNotification* notification){
NSData * data = [file readDataToEndOfFile];
NSString * string;
string = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
NSLog(@"Result: %@", string);
}];
}
这些任务与您的代码在不同的进程中运行,即异步运行。到稍后两行到达readDataToEndOfFile
时,它们可能还没有完成(甚至可能还没有启动!)。
[如果您已经在后台线程上,则可以轮询其状态:while( ![task isRunning]){
,或者如果您在主线程上,我建议使用GCD将其放入队列并在那里进行轮询。
实际上,比使用通知更好:
[task3 launch]; [[NSNotificationCenter defaultCenter] addObserverForName:NSTaskDidTerminateNotification object:task3 queue:nil usingBlock:^{ NSData * data = [file readDataToEndOfFile]; NSString * string; string = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding]; NSLog(@"Result: %@", string); }];
请参见TN2050: Observing Process Lifetime Without Polling。每个
NSTask
终止时都会发送NSTaskDidTerminateNotification
(理想情况下,您应该检查其返回码,而不是假设其已成功运行)。您可以创建一个在task3
发送该通知时运行的块。
以下代码对我有用。
大约8年后,我认为grep二进制文件不在/ usr / bin中,对我来说,它在/ bin中。另外,对于awk命令,将启动路径设置为grep。